Yanmar 3JH4E Service Manual page 35

2) If necessary, adjust the V-belt tension (deflection).
To adjust the V-belt tension, loosen the set bolt for
the belt adjuster and move the alternator to tighten
the V-belt.
3) Visually check the V-belt for cracks, oiliness or
wear. If any, replace the V-belt with new one.
[Notice]
When the V-belt will be replaced with new one,
loosen the set bolt and move the alternator and also
loosen the V-pulley set bolts for the cooling water
pump. Remove the V-belt.
After replacing with a new V-belt and adjusting the
tension, run the engine for 5 minutes and readjust the
deflection to the value in the table above.
(5) Adjusting the intake/exhaust valve clearance
Make measurement and adjustment while the engine is cold.
1) Valve clearance measurement
a) Remove the rocker arm cover above cylinder
head.
b) Set the No.1 cylinder in the compression TDC
Turn the crankshaft to bring the piston of the
No.1 cylinder to its compression top dead center
while watching the rocker arm motion, the timing
mark of the flywheel housing and the top mark of
the flywheel.
(Position where both the intake and exhaust
valves are closed.)
(Notes)
• The crankshaft shall be turned clockwise as seen
from the gear case side.
• The No.1 cylinder position is on the opposite side of the gear case.
• Since there is a clearance between the rocker arm and valve at the compression top dead center, the
position of TDC can be checked by hand Also see that the top mark on the flywheel aligns with the
mark on the flywheel housing. If there is no valve clearance, disassemble and inspect around the
valve seat, since the valve seat may be worn abnormally.
Set bolt
Adjuster
Alternator
(Tension adjustment)
Injection
timing marks
No.1 cylinder
T.D.C.
Flywheel
19
2. Inspection and Adjustment
Belt adjuster
Alternator
Adjust the V-belt tension
inserting a bar
Flywheel
housing
Hole